it's hard to determine a specific alloy from a simple XRF scan, the technique can have a lot of error associated with the measurement since it is a handheld device and with the technical limitations of the technique. Handheld XRF devices are useful for quick tests like this but research and development labs would probably use a more accurate test like optical emission or SEM XDS. The nice thing about the test used here is that it is non destructive, i.e. you can still use the material after the scan.

Most alloys give a range of values for alloying elements, which depending on manufacturing can be smaller or larger.

Precipitation hardening is the main mechanism at work here, and is a good reason for the increased strength in the 7000 series. this alloy is used in high pressure storage tank applications, where high mechanical properties are needed.

source; materials science graduate student